This invention relates to a hydraulic unit. More specifically, this invention relates to a three position servo system that controls the displacement of a hydraulic motor.
Many types of mobile equipment use a two displacement hydraulic motor resulting in two distinct vehicle speed ranges. As the upper speed goals of these machines increase as part of periodic machine redesign projects, there becomes a larger and larger gap between the high and low speed ranges. Thus, a need for an intermediate speed range is desired.
Additionally, there are certain considerations that need to be taken into account if additional distinct speed ranges are to be added. Specifically, dual path machines (such as crawlers or skid steer loaders) will require a high degree of accuracy in any type of intermediate position in order to avoid mistracking problems.
Therefore, a principal object of the present invention is to provide a three position servo system to control the displacement of a hydraulic motor.
Yet another object of the present invention is to provide a multiple position servo system that provides optimal accuracy.
These and other objects, features or advantages of the present invention will become apparent from the specification and claims.